Microstructure arrangement for gripping low coefficient of friction materials

ABSTRACT

A microstructure arrangement having a substrate; a first set of pillars having a cross section area in the range of 10 μm2 to 400 μm2 and a pitch in the range of 20 μm to 1000 μm; a second set of pillars disposed on said first set of pillars having a cross section area less than that of the pillars in said first set of pillars; wherein said second set of pillars are defined by pillars each having a cross section width from 0.5 μm to 100 μm and a pitch in the range of 1 μm to 200 μm; and, wherein said first and second set of pillars are configured to cooperate to have a physical property of a grip force in excess of 50.0N with a contact area of 25% or less, as determined by the friction testing method.

RELATED REFERENCES

This application is a continuing application from U.S. patentapplication Ser. No. 16/451,741 filed Jun. 25, 2019 which is acontinuation from U.S. patent application Ser. No. 15/674,291 filed Aug.10, 2017 (now U.S. Pat. No. 10,377,044 issued Aug. 13, 2019) whichclaims priority from U.S. Provisional Patent Application 62/372,896filed Aug. 10, 2016, all of which are incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to microstructure patterns, and moreparticularly, to a gripping surface having a microstructure patternadapted for improving grip on low coefficient of friction materials.

Polymer materials with low coefficient of friction (COF), such as PTFE,HOPE, nylon or POM, are manufactured into devices to allow easy slidingof devices with or without a lubricant being present. Typical examplesinclude a PTFE shaft seal sliding against a polycarbonate housing; anylon covered vascular catheter sliding through a polypropyleneintroducer tube, or a PTFE coated guide wire sliding inside a PTFE linedvascular catheter. However, these low COF items must also be grippedduring manufacturing, or during use, or during disassembly and disposal.Particularly during manufacturing and use, gripping the item must bedone carefully to prevent causing damage or degradation, such ascreating scratches or generating contaminating particles. During highvolume manufacturing, automated gripping of these materials isdesirable. Current solutions for gripping low COF materials arecumbersome and require mechanical methods such as holes, slots orthreads; or they accept low levels of grip force and delicateoperations. It is also difficult to grip low COF rubbery polymers suchas silicone rubber or human skin. Previous attempts to address theseproblems include unsatisfactory use of additives that results in“sticky” surfaces or use adhesives which are undesirable as they can betoo sticky, create unnecessarily rough surfaces, and can cause pain tothe user. The unmodified material can have a COF of 0.2 or less.

Accordingly, it is an object of the present invention to provide amicrostructure arrangement on a gripping surface capable of firmlygripping low COF materials without causing damage to the material.

SUMMARY OF THE INVENTION

Gripping, moving and manipulating devices made of low COF polymer bydevices with a gripping pad is improved by forming a pattern ofmicrostructure features according to the present invention on at leastone surface of the gripping pad. Coefficient of friction greater than0.90 was achieved using patterns of microstructure arrays covering thegripping pad and molded in a material with a Young's modulus greaterthan the Young's modulus of the material being gripped. Microstructureshaving a width greater than 2 microns and less than 500 microns were themost effective at providing grip on low COF materials such as PTFE. Someof the most effective gripping occurred when contact is less than about25% and greater than about 0.25%. The microstructure features canfurther consist of one array stacked on another array of largermicrostructure features, which further improves grip.

The invention can include a microstructure arrangement for gripping lowcoefficient material comprising: a substrate disposed on a grippingsurface wherein the unmodified substrate has a coefficient of frictionrelative to a polymer against steel of 0.2 or less; a first set ofpillars disposed on the substrate having a cross section area per pillarin the range of 100 μm2 to 160,000 μm2, height relative to the substratein the range of 10 μm to 400 μm, and a pitch determined from the centerof the pillars in the range of 20 μm to 1000 μm; a secondary set ofpillars disposed on the first set of pillars having a cross section arealess than that of the pillars in the first set of pillars; and, whereinthe first set of pillars and the second set of pillars are configured tocooperate to have the physical property of a grip force in excess of50.0N with a contact area of 25% or less as determined by the frictiontesting method. The contact area is defined as the area of the outermosttop surface of the outmost set of pillars. This is the area in contactif a rigid flat plaque of material is brought in contact with the micropattern surface under low pressure. The grip force can be in excess of55.0N with a contact area of 20% or less. The first set of pillars andthe second set of pillars can be configured to cooperate to have thephysical property touch aesthetic that are painless and prickly asdetermine by the tactile testing method. The grip force can exceed 60.0Nwith a contact area of 10% or less. The first set of pillars and thesecond set of pillars can be configured to cooperate to have acoefficient of friction in the range of 0.7 to 0.9 when the substrate isPTFE. The first set of pillars and the second set of pillars can beconfigured to cooperate to have a coefficient of friction greater than3.4 times smooth PTFE. The first set of pillars and the second set ofpillars can be configured to cooperate to have a coefficient of frictionin the range of to 1.4 when the substrate is SBR. The first set ofpillars and the second set of pillars can be configured to cooperate tohave a coefficient of friction greater than 1.1 times smooth SBR. Thefirst set of pillars and the second set of pillars can be configured tocooperate to have a coefficient of friction in the range of 0.8 to 1.0when the substrate is nylon. The first set of pillars can be arranged ina rectangular lattice or triangular lattice. The secondary pattern canbe disposed on top of the primary pillars in a consistent pattern of onethat varies from pillar to pillar.

BRIEF DESCRIPTION OF THE DRAWINGS

The construction designed to carry out the invention will hereinafter bedescribed, together with other features thereof. The invention will bemore readily understood from reading the following specification and byreference to the accompanying drawings forming a part thereof, whereinan example of the invention is shown and wherein:

FIGS. 1A-1F shows micrograph images of a microstructure arrangementincluding a plurality of pillars on a gripping surface materialaccording to the present invention;

FIG. 1G shows a micrograph image of a microstructure arrangementincluding a plurality of recesses on a gripping surface materialaccording to the present invention;

FIGS. 2A-2B shows micrograph images of a microstructure arrangementincluding a plurality of primary microstructure pillars carrying aplurality of secondary microstructure pillars on a gripping surfacematerial according to the present invention;

FIG. 3 shows a schematic for one testing method according to the presentinvention;

FIG. 4 shows a schematic for one testing method according to the presentinvention;

FIG. 5 shows a schematic for one testing method according to the presentinvention;

FIGS. 6A to 6B show testing results with a 20N force applied to atesting sample;

FIGS. 6C to 6D show testing results with a 50N force applied to atesting sample;

FIGS. 6E to 6F show testing results with an 80N force applied to atesting sample;

FIG. 6G shows testing results with a 110N force applied to a testingsample;

FIG. 6H shows testing results with a 140N force applied to a testingsample;

FIG. 7 shows a graphical representation of some of the novel physicalproperties and aspects of the present invention;

FIG. 8A shows a perspective view of aspects of the present invention;and,

FIG. 8B shows a top down view of aspects of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to the drawings, the invention will now be described inmore detail. According to the present invention, the microstructurearrangements detailed herein are applied, in one embodiment, to agripping pad made of a high modulus material. The gripping pad can havea higher Young's modulus than the material to be gripped. At least oneouter surface of the gripping pad contains a microstructure patternconsisting of, for example, micro pillar structures, or alternativemicrostructure recesses, that exhibit high grip and high coefficient offriction (COF) to plastic polymer materials that have low COF such aspolytetrafluoroethylene (PTFE) or low COF rubber polymers such assilicone rubber or human skin.

In one embodiment, the microstructure pattern may be formed in a pad ofsteel, with a resulting increase in COF of steel to PTFE from 0.2 toover 0.8. In one embodiment, the microstructure pattern may be formed ina pad of high modulus polymer, such as polyester terephthalate (Mylar)or modified polyester terephthalate (Dupont Hytrel or Eastman Tritan),with a resulting increase in COF of polyester terephthalate to PTFE fromabout 0.04 to over 1.00 without visible damage to the PTFE. Thesematerials are provided by way of example only, as the microstructurearrangements according to the present invention can be included invarious other materials as would be understood by a person of ordinaryskill in the art.

The microstructure pattern described and illustrated herein may beformed in a pad of steel or high modulus polymer that grips any lowermodulus polymer material with a COF greater than 0.8 without visibledamage.

The microstructure pattern described and illustrated herein may beformed in a pad of steel or high modulus polymer that grips biopolymersincluding skin with pull force greater than 50 Newtons without visibledamage or the perception of pain.

The microstructure pattern described and illustrated herein may beformed in a pad of steel or high modulus polymer that grips textiles andfabric with a COF greater than 1.00 without visible damage to thefabric.

In one embodiment, the microstructure pattern includes micro pillarswith an angle of orientation to a film base material of greater than 75degrees, and preferred greater than 85 degrees.

In illustrated embodiments, referring to FIGS. 1A-1G, the microstructurepattern includes primary microstructure features defined by pillars thatmay be of a cross section that is circular, square, triangular, circularfluted, rectangular or other geometric shapes, and combinations thereof.The illustrated embodiments described herein are provided by way ofexample only and are not limiting of the various geometric shapes thatmay be utilized in the present invention.

In one embodiment, the microstructure pattern includes micro pillarsthat include an upper end that may be flat, rounded, spherical,pyramidal or have smaller pillars on the end surface of the largerpillar, such as illustrated in FIGS. 2A-2F. The stacked arrangement isparticularly useful in gripping skin, rubber and other softer materials.

Referring to FIGS. 2A-2B, in the illustrated embodiments, themicrostructure pattern includes a primary microstructure with asecondary microstructure feature carried on top of the primarymicrostructure feature. In the embodiment shown in FIGS. 2A-2B, thesecondary microstructure 40 is defined by smaller pillars covering thetops of larger pillars defining the primary microstructure 38. In oneembodiment, the smaller pillars may have a cross section width from 0.5to 100 microns, a height above the end of the primary pillar from 1 to100 microns tall, and a center to center pitch of 1 to 200 microns,oriented in a triangular, rectangular or random distribution, orcombinations thereof, over the outer end surface of the larger pillar.The illustrated embodiments described herein are provided by way ofexample only, and are not limiting of the various geometric shapes thatmay be utilized in defining the primary and secondary microstructures ofthe present invention.

In one embodiment, the microstructure pattern will cover greater than25% of the outer surface area of at least one side of the gripping pad.

The microstructure pattern can be formed on a variety of gripping padsurfaces for a variety of applications, including, for example, on asingle or pair of rotating wheels to provide grip, on finger tips orpalms of gloves, on brake pads and brake drums or rotors, on clutchplates, on jaws of pliers, graspers, retractors and similar squeezinginstruments, on robotic surgical tools or laparoscopic surgical tools.The gripping pad surfaces can be in the form of tapes and films forwrapping handles or for adhering to surfaces and they can be moldedforms such as handles of tools. The gripping pads can be molded forarticles that can include handles, grips, labels, closures, utensils,and similar objects that can be gripped by hand or with a hand coveringsuch as a glove. The gripping pads may be sewn to or molded into gloves,luggage grip, backpack straps and similar items. The gripping pads maybe molded or printed on labels and containers. These are but a fewexamples of the possible application of the microstructure patterndetailed herein.

Low COF polymers to which the microstructure pattern can be applied toimprove grip include, but are not limited to, PTFE, HOPE, PE, PP, nylon,PET or any similar plastic polymer, silicone rubber, isoprene rubber,thermoplastic elastomers, polyurethane rubbers or any similar rubberpolymer. These low COF polymers can have a COF against smooth steel lessthan 0.2, however, a gripping pad including a microstructure patternaccording to the present invention can securely grip and hold suchmaterials.

Preferably, the primary microstructures (and secondary microstructuresin a stacked array embodiment) have a uniform height from the film baseso that a uniform pressure is applied against the surface of thematerial to be gripped. This prevents damage to the material whileproviding optimal grip by allowing all of the microstructure ends toengage the material in a uniform engagement.

Table 1 below lists dimensional specifications of the patterns testeddirected to certain arrangements of micro patterns on gripping surface.

SHAPE (pillar unless Pattern otherwise % ID SIZE (μm) noted) PITCH(μm)LATTICE DEPTH (μm) Contact H190AP 200 circular 500 rectangular 600 12.6%H185AP 100 circular 700 rectangular 200 1.6% H191AP 150 circular 450rectangular 450 8.7% H282AP 25 × 50 elipse 150 rectangular 70 5.6%H034AP 30 circular 85 rectangular 40 9.8% H037AP 50 circular 140rectangular 40 10.0% H002AP 50 circular 100 rectangular 70 19.6% H003AP50 × 25 oval 100 rectangular 70 9.8% H012CP 25 square 50 triangular 5025.0% H008AP 200 circular 400 triangular 350 22.7% H008AH 200 circular400 triangular 350 77.3% (holes) H009AP 100 circular 200 triangular 20022.7% H021AP 100 square 350 triangular 400 9.4% H160AP 10 + 100 circular20 + 200 triangular   20 + 200 5.0% H374AP 41 × 20.5 + 200 oval & 82 +933 rectangular 57.4 + 100 0.5% square H375AP 41 × 20.5 + 200 oval &82 + 660 rectangular 57.4 + 100 0.9% square H376AP 41 × 20.5 + 200 oval& 82 + 443 rectangular 57.4 + 100 2.0% square H377AP 41 × 20.5 + 200oval & 82 + 362 rectangular 57.4 + 100 3.0% square H378AP 41 × 20.5 +200 oval & 82 + 280 rectangular 57.4 + 100 5.0% square H379AP   41 ×20.5 oval 82 rectangular 57.4 9.8% H404AP 100 circular 200 rectangular50 19.6% H401AP 50 square 100 rectangular 25 25.0% H049AP 50 raised 200lines 75 25.0% (ridges)

The pillars can include a rounded cross section such as a circle, oval,square with rounded corners, or rectangle with rounded corners. Thepatterns can include the characteristics shown in the following table:

Calculated Width Height/Depth Pitch percent L1 + L2 L1 + L2 L1 + L2contact Pattern Shape (pillars) (μm) (μm) (μm) Lattice area H374AP oval& square 41 × 20.5 + 200 57.4 + 100 82 + 933 rectangular 0.45% H375APoval & square 41 × 20.5 + 200 57.4 + 100 82 + 660 rectangular  0.9%H376AP oval & square 41 × 20.5 + 200 57.4 + 100 82 + 443 rectangular  2% H377AP oval & square 41 × 20.5 + 200 57.4 + 100 82 + 362rectangular   3% H378AP oval & square 41 × 20.5 + 200 57.4 + 100 82 +280 rectangular   5% H379AP oval 41 × 20.5 57.4 82 rectangular  9.8%H002AP round 41 57.4 82 rectangular 19.6% H404AP circular 82 41 164rectangular 19.6% H401AP square 41 20.5 82 rectangular  25% H049APridges 41 61.5 164 lines  25% H008AH Circular (holes) 164 287 328triangular 77.3% Blank N/A N/A N/A N/A N/A 100

Referring to FIG. 1A, micro pattern H012CP is shown molded in stainlesssteel and includes an arrangement of square, rounded and oval shapedmicro pillars 10 that, as shown, in an offset pattern with a first line12 offset from a second line 14 resulting in a triangular lattice 16. InFIG. 1B, micro pattern H002AP is shown molded in stainless steel andincludes an arrangement of mostly rounded shaped micro pillars 18. Thepillars can be arranged in rows 20 a and 20 b referred to as arectangular lattice 22. In FIG. 1C, micro pattern H003AP is shown moldedin stainless steel and includes an arrangement of mostly oval shapedmicro pillars 24 in offset rows with a triangular lattice. In FIG. 1D,micro pattern H008AP is shown molded in stainless steel and includes anarrangement of highly uniform rounded shaped micro pillars. Micropattern H009AP (not pictured) is similar to the image in FIG. 1D ofmicro pattern H008AP except with slightly reduced dimension. The pillars26 of this figure are rounded in an offset pattern and have generallyuniform dimensions among the pillars. In FIG. E, micro pattern H021AP isshown molded in stainless steel and includes an arrangement of mostlysquare shaped micro pillars 28. In FIG. 1F, micro pattern H021AP alsoshown, but molded in Hytrel and includes an arrangement of mostly squareshaped micro pillars 30 in an offset design. In FIG. 1G, micro patternH008AH is shown molded in stainless steel and includes an arrangement ofrounded holes 32 in the substrate 34. The holes can be arranged in arectangular pattern. In referring to the dimensions, the depth of theholes are from the top of the substrate to the bottom of the hole, asopposed to referring to the height of the pillar relative to thesubstrate. In FIG. 2A, micro pattern H160AP is shown at 200×magnification as molded in stainless steel and includes an arrangementof rounded shaped micro pillars 38 arranged in an offset pattern. Aplurality of secondary and generally smaller micro pillars 40 can bedisposed on the top of the larger micro pillars 38. FIG. 2B is micropattern H160AP shown at 500× magnification to illustrate the arrangementof the smaller micro pillars 40 arranged on the tops of the larger micropillars 38. In one embodiment, the smaller micro pillars 40 can also bedisposed along the sides of the pillars and on the substrate 42.

In one embodiment, the micro patterns were etched on silicon wafers,transferred to silicone rubber, molded into a powdered metal/bindercompound, such as BASF Catamold 17-4 PH or 1001 steels, or into theplastic or rubber materials. In one embodiment, the molded powderedmetal compound can be sintered to create the micro patterns on the steelsurfaces. Some of the patterns can be modified using, electricaldischarge machining, laser etching, or CNC milling and sawing to createadditional features on the surface. Some methods of manufacturing aredescribed in U.S. Pat. No. 8,720,047 incorporated by reference.

Referring to FIG. 3, a weighted testing method is shown. A clamp havinga first jaw 44 a and a second jaw 44 b that can apply clamping forceagainst a weighted member 46 having an outer surface 48. The innersurface 50 of the jaws can contact the outer surface of the weightedmember and when the weighted member is pulled in a direction shown as52, the friction between the weighted member and the clamp can bemeasured. Different gripping materials can be attached to the clamp jawsand the friction results can be measured as shown in the following tablewith the gripping levels arranged into three categories: (low, medium orhigh).

Gripping 40A material PTFE Silicone PET TPE Dry Skin PP PS Sandpaper LowMedium Medium High Strength Medium Low Tape Tacky Foam Low Low LowSerrated Pliers High With Medium High With Low High With High WithDamage Damage Damage Damage Smooth 17-4PH Low High Low Low Low Low LowSteel Smooth Medium High High High Low High Silicone (40A) H012AP In 17-High Low High High Low High High 4PH Steel H012AP In Low Low Low Low LowLow Low Polypropylene H160AP In 17- High High High High High High High4PH Steel

Referring to FIG. 4, the tactile properties of the various patterns weremeasured using a tactile testing method. Using this method, micropatterns were machined on a steel sample, a 1×1 inch samples in oneembodiment with a blank sample of like dimensions used as a control. Thesample 54 is held in clamp 56 which is in turn attached to a load cell58. The load cell can be a 251b load cell such as an S type or S-Beamload cell as provided by Omega Engineering, Inc. A test subject wasasked to grip the sample. The load cell is fixed to an anchor point 60,in one embodiment. The test subject then grips the sample and pulls thesample generally in a direction shown as 62 and is requested to providetest results concerning the touch aesthetic as shown for each materialand pattern in the following table.

Touch Aesthetic Touch Aesthetic soft materials hard materials Pattern(Silicone, (Steel, Depth $ ID TPE, TPU) Polypropylene) (μm) ContactH190AP soft, fuzzy, Painful 600 12.6% painless H185AP painless, Painful200 1.6% prickly H191AP soft, fuzzy Painful 450 8.7% painless H282APsmooth, painless Comfortable 70 5.6% H034AP painless Comfortable 40 9.8%H037AP painless Comfortable 40 10.0% H002AP painless, smooth Comfortable70 19.6% H003AP painless, smooth Comfortable 70 9.8% H012CP painless,smooth Comfortable 50 25.0% H008AH smooth Comfortable 22.7% H008APprickly Painful 350 77.3% H009AP prickly Comfortable 200 22.7% H021APsoft, fuzzy, Painful 400 9.4% painless H160AP smooth, painlessComfortable   20 + 200 5.0% H374AP prickly Comfortable 57.4 + 100 0.5%H375AP prickly Comfortable 57.4 + 100 0.9% H376AP prickly Comfortable57.4 + 100 2.0% H377AP prickly Comfortable 57.4 + 100 3.0% H378APprickly Comfortable 57.4 + 100 5.0% H379AP smooth, painless Comfortable57.4 9.8% H404AP smooth, painless Comfortable 50 19.6% H401AP smooth,painless Comfortable 25 25.0% H049AP rigid, painless Comfortable 7525.0%

The grip force that was measured using the load cell with themeasurement of the force on the sample required is pulled by the testsubject until the samples slipped from between the fingers of the testsubject. The peak force was measured in Newtons (N) for multiple trialsand the average values (Average) and standard deviation calculated (SD)as shown below.

Grip Force in Newtons Pattern ID (% Contact) Trial 1 Trial 2 Trial 3Average SD H374AP (0.45%) 66 65 64 65.0 0.8 H375AP (0.9%) 75 72 69 72.02.4 H376AP (2%) 78 74 75 75.7 1.7 H377AP (3%) 76 74 71 73.7 2.1 H378AP(5%) 75 73 72 73.3 1.2 H379AP (9.8%) 68 67 66 67.0 0.8 H002AP (19.6%) 5957 56 57.3 1.2 H404AP (19.6%) 55 58 58 57.0 1.4 H401AP (25%) 51 53 5352.3 0.9 H049AP (25%) 44 44 48 45.3 1.9 H008AH (77.3%) 44 46 45 45.0 0.8Blank (100%) 42 37 39 39.3 2.1Referring to FIG. 7, the graphical representation of this chart is shownfor various patterns, one aspect of the novelty of the present inventioncan be shown. Conventional belief is that to accomplish sufficientfriction between skin and an object, a contact area of twenty percent(20%) or more is needed. The contact area is the area of the finger,such as the fingertip, that is in contact with the surface. The presentinvention shows that with the micro patterns shown herein, the gripforce (in Newtons) significantly increases with contact area between0.25% and 25% as shown in section 72.

Materials tested for providing the samples using in the tactile testingincluded 17-4 PH stainless steel, Eastman Tritan modified PET, DupontHytrel modified PET, Momentive silicone rubber, 70 Shore A, NuSilsilicone 40 Shore A. Low COF materials used in the tactile testingincluded polytetrafluoroethylene (PTFE), polyethylene (PE),polypropylene (PP), nylon, polyacetal resin (POM), polystyrene,polyesterterephthalate (PET), silicone rubber and human skin.

Referring to 5, the friction testing method is shown. The sample 54 isprovided with a blank of the same or generally the same dimension as acontrol. The sample is secured between first clamping member 56 a andsecond clamping member 56 b and force applied in the respectivedirections 58 a and 56 b against the sample. The sample can havemicrostructures on the outer sides that can contact the clampingmembers. The force that is applied to the sample can be measured with aforce gauge 60. The force gauge can be a NEXTECH 1000N model in oneembodiment. The force applied to the sample between the clamping memberscan be tested at several levels or contact forces, including incrementsof 20N, 50N, 80N, 110N, and 120N. The sample can be retracted indirection 62 by retractor 64 with load cell 66 disposed between thesample and the retractor. The retraction rate can be 1 mm/second. Thetesting was performed, and the averages tabulated as shown below inFIGS. 6A through 6J. The sample and load cell can be removably connectedwith connector 70, in one embodiment. The results of the friction testfor certain materials and patterns are shown in the following table:

Coefficient of Friction for Each Material Pattern ID PTFE SBR NylonSilicone Rubber smooth 0.2 1.0 0.3 1.1 H374AP 0.7 1.3 1.0 1.0 H375AP 0.81.2 1.0 1.0 H376AP 0.9 1.4 0.9 1.1 H377AP 0.8 1.3 0.8 1.1 H378AP 0.7 1.30.8 1.1 H379AP 0.8 1.3 0.8 1.2

In the above table, the materials shown are polytetrafluoroethylene(PTFE), styrene-butadiene rubber (SBR), nylon and silicone rubber.

Referring to FIGS. 8A and 8B, the pattern designated H376AP is shownhaving a substrate 42 with a primary pattern 38 that can include asecondary pattern 40 disposed on the top of other outer surface of theprimary pattern. The secondary pattern can be generally consistent frompillar to pillar of the primary pattern or can vary from pillar topillar as illustrated. The rows can be inline (rectangular lattice) oroffset (triangular lattice).

The invention can include a microstructure arrangement for gripping alow coefficient of friction material comprising: a substrate disposed ona gripping surface wherein the substrate has a higher Young's modulusthan the low coefficient of friction material to be gripped; a first setof pillars disposed on the substrate with each pillar having a crosssection area in the range of 10 μm2 to 400 μm2, a height relative to thesubstrate in the range of 10 μm to 400 μm, and a pitch determined fromthe center of the pillars in the range of 20 μm to 1000 μm; a second setof pillars disposed on said first set of pillars with each pillar ofsaid second set of pillars having a cross section area less than that ofthe pillars in said first set of pillars; wherein said second set ofpillars are defined by pillars each having a cross section width from0.5 μm to 100 μm, a height of from 1 μm to 100 μm, and a pitchdetermined from the center of the second set of pillars in the range of1 μm to 200 μm; wherein said first and second set of pillars areconfigured to cooperate to have the physical property of a grip force inexcess of 50.0N with a contact area of 25% or less, as determined by thefriction testing method; and, wherein said first and second set ofpillars are configured to cooperate to have a coefficient of friction inthe range of about 0.7 to about 1.4.

The microstructure arrangement can include a grip force is in excess of55.0N with a contact area of 20% or less. The microstructure arrangementcan include a grip force in excess of 60.0N with a contact area of 10%or less. The microstructure arrangement can include a substrate formedfrom the material selected from the group consisting of steel, polyesterterephthalate, and modified polyester terephthalate. The microstructurearrangement can include a substrate of steel and the material to begripped is polytetrafluoroethylene, and wherein said substrate with saidfirst and second set of pillars has a coefficient of friction in therange of 0.7 to 0.9 against said polytetrafluoroethylene. Themicrostructure arrangement can include a substrate of steel and thematerial to be gripped is styrene-butadiene rubber, and wherein saidsubstrate with said first set and second of pillars has a coefficient offriction of about 1.4 against said styrene-butadiene rubber. Themicrostructure arrangement can include a substrate of steel and thematerial to be gripped is Nylon, and wherein said substrate with saidfirst and second set of pillars has a coefficient of friction of about1.0 against said Nylon. The microstructure arrangement can include afirst set of pillars having an angle of orientation to said substrate ofgreater than 75 degrees.

The microstructure arrangement for gripping a low coefficient offriction material can include a substrate disposed on a gripping surfacewherein the substrate has a higher Young's modulus than the lowcoefficient of friction material to be gripped, and wherein thesubstrate has a coefficient of friction relative to a polymer againststeel of about 0.2 or less without any microstructure arrangement; atleast a first set of pillars carried on the substrate with each pillarhaving a cross section area in the range of 10 μm2 to 400 μm2, a heightrelative to the substrate in the range of 10 μm to 400 μm, and a pitchdetermined from the center of the pillars in the range of 20 μm to 1000μm; and, wherein the at least said first set of pillars define amicrostructure arrangement on said substrate configured to provide acoefficient of friction in the range of about 0.7 to about 1.4 against apolymer with said substrate made of steel.

The material to be gripped can be selected from the group consisting ofpolytetrafluoroethylene, styrene-butadiene rubber, nylon, high-densitypolyethylene, polyethylene, polypropylene, polyester terephthalate,polyacetal resin, silicone rubber, isoprene rubber, thermoplasticelastomers and polyurethane rubbers. The microstructure arrangement caninclude at least said first set of pillars covers at least about 25% ofthe surface area of a gripping side of said substrate. Themicrostructure arrangement can include a first set of pillars have agenerally uniform height from the surface of said substrate.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which the presently disclosed subject matter belongs.Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresently disclosed subject matter, representative methods, devices, andmaterials are herein described.

Unless specifically stated, terms and phrases used in this document, andvariations thereof, unless otherwise expressly stated, should beconstrued as open ended as opposed to limiting. Likewise, a group ofitems linked with the conjunction “and” should not be read as requiringthat each and every one of those items be present in the grouping, butrather should be read as “and/or” unless expressly stated otherwise.Similarly, a group of items linked with the conjunction “or” should notbe read as requiring mutual exclusivity among that group, but rathershould also be read as “and/or” unless expressly stated otherwise.

Furthermore, although items, elements or components of the disclosuremay be described or claimed in the singular, the plural is contemplatedto be within the scope thereof unless limitation to the singular isexplicitly stated. The presence of broadening words and phrases such as“one or more,” “at least,” “but not limited to” or other like phrases insome instances shall not be read to mean that the narrower case isintended or required in instances where such broadening phrases may beabsent.

It will be understood by those skilled in the art that one or moreaspects of this invention can meet certain objectives, while one or moreother aspects can meet certain other objectives. Each objective may notapply equally, in all its respects, to every aspect of this invention.These and other objects and features of the invention will become morefully apparent when the detailed description is read in conjunction withthe accompanying figures and examples.

It is to be understood that the summary of the invention and thedetailed description are of a preferred embodiment and not restrictiveof the invention or other alternate embodiments of the invention. Inparticular, while the invention is described herein with reference to anumber of specific embodiments, it will be appreciated that thedescription is illustrative of the invention and is not constructed aslimiting of the invention. Various modifications and applications mayoccur to those who are skilled in the art, without departing from thespirit and the scope of the invention, as described by the appendedclaims. Likewise, other objects, features, benefits and advantages ofthe present invention will be apparent from this summary and certainembodiments described below, and will be readily apparent to thoseskilled in the art. Such objects, features, benefits and advantages willbe apparent from the above in conjunction with the accompanyingexamples, data, figures and all reasonable inferences to be drawntherefrom, alone or with consideration of the references incorporatedherein.

While the present subject matter has been described in detail withrespect to specific exemplary embodiments and methods thereof, it willbe appreciated that those skilled in the art, upon attaining anunderstanding of the foregoing may readily produce alterations to,variations of, and equivalents to such embodiments. Accordingly, thescope of the present disclosure is by way of example rather than by wayof limitation, and the subject disclosure does not preclude inclusion ofsuch modifications, variations and/or additions to the present subjectmatter as would be readily apparent to one of ordinary skill in the artusing the teachings disclosed herein.

What is claimed is:
 1. A microstructure arrangement for gripping a lowcoefficient of friction material comprising: a substrate disposed on agripping surface; a first set of pillars disposed on the substrate witheach pillar having a cross section area in the range of 100 μm² to160,000 μm² and a pitch determined from the center of the pillars in therange of 20 μm to 1000 μm; a second set of pillars disposed on saidfirst set of pillars with each pillar of said second set of pillarshaving a cross section area less than that of the pillars in said firstset of pillars; wherein said second set of pillars are defined bypillars each having a cross section width from 0.5 μm to 100 μm and apitch determined from the center of the second set of pillars in therange of 1 μm to 200 μm; and, wherein said first and second set ofpillars are configured to cooperate to have the physical property of agrip force in excess of 50.0N with a contact area of 25% or less, asdetermined by the friction testing method.
 2. The microstructurearrangement of claim 1 wherein the first set of pillars includes aheight relative to the substrate in the range of 10 μm to 400 μm.
 3. Themicrostructure arrangement of claim 1 wherein the second set of pillarsincludes a height of from 1 μm to 100 μm.
 4. The microstructurearrangement of claim 1 wherein said first and second set of pillars areconfigured to cooperate to have a coefficient of friction in the rangeof about 0.7 to about 1.4.
 5. The microstructure arrangement of claim 1wherein said grip force is in excess of 55.0N with a contact area of 20%or less.
 6. The microstructure arrangement of claim 1 wherein the gripforce in excess of 60.0N with a contact area of 10% or less.
 7. Themicrostructure arrangement of claim 1 wherein said substrate is carriedby a surface of one of a wheel, finger tips of a glove, palm of a glove,brake pad, brake drum, brake rotor, clutch plate, plier, grasper,retractor, surgical tools, laparoscopic tool and any combinationthereof.
 8. The microstructure arrangement of claim 1 wherein saidsubstrate is a steel.
 9. The microstructure arrangement of claim 1wherein said substrate is a polymer.
 10. The microstructure arrangementof claim 1 wherein the substrate is steel and the material to be grippedis Nylon, and wherein the substrate with the first and second set ofpillars has a coefficient of friction of about 1.0 against the Nylon.11. The microstructure arrangement of claim 1 wherein the first set ofpillars have an angle of orientation to the substrate of greater than 75degrees.
 12. The microstructure arrangement of claim 1 wherein thematerial to be gripped is a human skin, and wherein the substrate withthe first and second set of pillars have pull force greater than 50 Nagainst the human skin.
 13. The microstructure arrangement of claim 12wherein said first and second set of pillars are configured to cooperateto have a coefficient of friction in the range of about 0.7 to about1.4.
 14. A microstructure arrangement for gripping a low coefficient offriction material comprising: a substrate disposed on a grippingsurface; a first set of pillars carried on the substrate with eachpillar having a height relative to the substrate in the range of 10 μmto 400 μm and a pitch determined from the center of the pillars in therange of 20 μm to 1000 μm; and, wherein the at least said first set ofpillars define a microstructure arrangement on said substrate configuredto provide a coefficient of friction in the range of about 0.7 to about1.4 against a polymer with said substrate made of steel.
 15. Themicrostructure arrangement of claim 14 wherein the first set of pillarshas a cross section area in the range of 10 μm² to 400 μm².
 16. Themicrostructure arrangement of claim 14 wherein the material to begripped is selected from the group consisting ofpolytetrafluoroethylene, styrene-butadiene rubber, nylon, high-densitypolyethylene, polyethylene, polypropylene, polyester terephthalate,polyacetal resin, silicone rubber, isoprene rubber, thermoplasticelastomers and polyurethane rubbers.
 17. The microstructure arrangementof claim 14 wherein said at least said first set of pillars covers atleast about 25% of the surface area of a gripping side of saidsubstrate.
 18. The microstructure arrangement of claim 14 wherein saidat least said first set of pillars have a generally uniform height fromthe surface of said substrate.
 19. A microstructure arrangement forgripping a low coefficient of friction material comprising: a substratedisposed on a gripping surface; a first set of pillars disposed on thesubstrate with each pillar having a height relative to the substrate inthe range of 10 μm to 400 μm and a pitch determined from the center ofthe pillars in the range of 20 μm to 1000 μm; a second set of pillarsdisposed on said first set of pillars with each pillar of said secondset of pillars having a cross section area less than that of the pillarsin said first set of pillars; wherein said second set of pillars aredefined by pillars each having a height of from 1 μm to 100 μm and apitch determined from the center of the second set of pillars in therange of 1 μm to 200 μm; and, wherein said first and second set ofpillars are configured to cooperate to have the physical property of agrip force in excess of 50.0N with a contact area of 25% or less, asdetermined by the friction testing method.
 20. The microstructurearrangement of claim 19 wherein the first set of pillars includes across section area in the range of 100 μm² to 160,000 μm².
 21. Themicrostructure arrangement of claim 19 wherein the second set of pillarsincludes a cross section width from 0.5 μm to 100 μm.
 22. Amicrostructure arrangement for gripping a low coefficient of frictionmaterial comprising: a substrate disposed on a gripping surface whereinthe substrate has a higher Young's modulus than the low coefficient offriction material to be gripped; a first set of pillars disposed on thesubstrate with each pillar having a cross section area in the range of100 μm² to 160,000 μm², a height relative to the substrate in the rangeof 10 μm to 400 μm; a second set of pillars disposed on said first setof pillars with each pillar of said second set of pillars having a crosssection area less than that of the pillars in said first set of pillars;wherein said second set of pillars are defined by pillars each having across section width from 0.5 μm to 100 μm, a height of from 1 μm to 100μm, and a pitch determined from the center of the second set of pillarsin the range of 1 μm to 200 μm; and, wherein said first and second setof pillars are configured to cooperate to have the physical property ofa grip force in excess of 50.0N with a contact area of 25% or less, asdetermined by the friction testing method.